1. Field of the Invention
Exemplary aspects of the present invention generally relate to an optical scanning apparatus and an image forming apparatus including the same, and more particularly, to an optical scanning apparatus which optically scans an object by using a light beam emitted from a light source such as a laser diode, and an image forming apparatus including the same.
2. Description of the Background Art
An optical scanning apparatus optically scans an object such as a photoreceptor or the like by using a light beam emitted from a light source, for example, a laser diode. This type of optical scanning apparatus, as disclosed for example in Japanese Patent Unexamined Application No. 2007-144952, has been known.
FIG. 15 is a side view illustrating a light source retainer of such an optical scanning apparatus. In FIG. 15, an LD unit 202 including a laser diode 201 (hereinafter referred to simply as LD) serving as the light source is mounted on an outer side surface 203 of a housing of the optical scanning apparatus. The LD 201 is press-fitted into an insertion hole provided to the LD unit 202 such that the optical beam can be emitted from a front side which is a plane of FIG. 15 toward a rear side. In FIG. 15, a direction perpendicular to the plane of FIG. 15 is an optical axis.
In FIG. 15, a circular opening, not shown, is formed at a portion of the housing side surface 203 behind the LD unit 202. Surrounding the circular opening is provided a cylindrical engaging portion disposed so as to protrude from the rear side of the plane of FIG. 15 to the front side.
A circular recessed portion, not shown, which engages the cylindrical engaging portion is provided to a surface of the LD, unit 202 facing the housing side surface 203. The circular recessed portion engages the cylindrical engaging portion of the housing side surface 203 so that the housing 203 holds the LD unit 202 in place.
The light beam emitted from the LD 201 in the above-described configuration enters the housing through the circular opening of the housing side surface 203. Subsequently, the light beam arrives at a surface of an object to be scanned, in this case a photoreceptor, via a polygon mirror, a focusing lens, and a reflective mirror, and so forth.
In such a configuration, in an effort to enable the outer peripheral surface of the cylindrical engaging portion of the housing to smoothly fit into the inner peripheral surface of the circular recessed portion of the LD unit 202, a small clearance is provided between the cylindrical engaging portion and the circular recessed portion. However, once so engaged, if the LD unit 202 rattles within the clearance, the optical scan position of the optical beam emitted from the LD 201 may fluctuate.
In an attempt to solve the above problem, a leaf spring 204 is provided to prevent the LD unit 202 from rattling. The leaf spring 204 is provided to bias the LD unit 202 in a direction perpendicular to the optical axis so that the circular recessed portion of the LD unit 202 is pressed against the cylindrical engaging portion of the housing side surface 203.
However, according to this configuration, leaf spring 204 manufacturing and/or installation error may cause the contact surface of the leaf spring 204 contacting the LD unit 202 to shift slightly away from the optical axis. Consequently, a force which causes the LD unit 202 to shift away from the optical axis is applied to the LD unit 202. As a result, a slight displacement of the position of the LD unit 202 occurs, causing the optical axis of the light beam emitted from the LD 201 to shift accordingly, so that precise optical scanning is difficult to perform.